It is not clear what to do with MSI for new users

[maks-rafalko]

Feedback from Slack: (dkarlovi)

what I think would do wonders is some actionable information what to do with the MSI number

after having just started using Infection, that wasn't anything to me (since I've never been exposed to MT tools before), it was just some number
what does MSI 30 mean? What does MSI 100 mean?
I didn't know

We need to think about writing an article in our docs that provides comprehensive information about what MSI does mean and how to treat it, what to do next after running Infection.

[sanmai]

From Slack:

We have a functional core which deals with things like permission checks, and whether some action is possible given current state.
Methods in the core a purely functional and are thus unit tested (as opposed to integration/functional tests on the rest of the app).
Then we run infection with 100% min MSI, but only over the functional core and only with unit tests.

This is because:

• It's impossible to get 100% MSI over other parts of the code base
• Running non-unit tests (ie. with database fixtures and booting Symfony) is waaaaay too slow with xdebug enabled

I think this gives us most of the benefits of infection but without the troubles of identifying which mutants we don't care about and the like.

[maks-rafalko]

Here is what I got in email, pasting as is:

just wanted to share some initial hurdles Im experiencing from a new user perspective.

- wow just ran the command and things happened.. awesome
- hmmm cool lots of red "M"s guess Ill have things to fix
- hmmm whats this json file and how do I view it?
- does it have a coverage viewer like phpunit coverage-html?
- lets run it again with some other options and see what happens to this md file
- hmmm only 2 red Ms now.. did it fix things for me?
- hmmm killed mutants sounds like I killed the bugs.. but docs say its failed tests

Anyways, not really a question.. just thought it would be valuable to share as sometimes when we work on projects for so long we forget what its like to be a new user and thats where the adoption happens.. Im determined to figure out the workflow and how to make my tests stronger.. still not sure how though haha.. i'll keep reading etc